Polyolefin treatment process for uniform crosslinking

Abstract

A process produces a block of polyolefin material with uniform crosslinking, which may be uniform between and within polymer chains in the polyolefin material. Steps include: providing an oven; placing the block into the oven; preheating the block to a uniform temperature above the melting point; further heating the block to a temperature at least 30 degrees Centigrade above the melting point; cooling the block to room temperature under an inert gas; and removing oxidized material from surface of the block. Optional steps include: subjecting the block to radiation before placing the block into the oven; removing the gases from the oven on a continuous or stepwise basis; controlling the purge gas flow out of the oven; and determining a heating time period for the block by subjecting control blocks to the same process and analyzing them after various heating times.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a continuation of U.S. application No. 12 / 986,163, filed 6, Jan. 2011, which is hereby incorporated by reference herein.TECHNICAL FIELD[0002]In the field of synthetic resins, a process of preparing a polyolefin using heat and / or wave energy to induce a physical and chemical reaction promoting uniform crosslinking in the polyolefin without changing the chemical composition of the polymer, without creating short polymer chains and enabling removal of oxidized polymer.BACKGROUND ART[0003]A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An olefin is also called an alkene with the general formula CnH2n and a polyolefin is also known as a polyalkene. Polypropylene is another common polyolefin which is made from the olefin propylene.[0004]By definition, cross-links are connecting points that link one polymer chain to ...

AI Technical Summary

Benefits of technology

The patent describes a process for creating a block of polyolefin material with uniform crosslinking. This means that the process results in a block that has the same level of crosslinking between polymer chains and within polymer chains. The process involves heating the block in an oven and controlling the heating to cause the carbon-carbon bond breakage within the microstructure. The block is then cooled and any oxidized material is removed from its surface. The process may also involve subjecting the block to radiation before heating and controlling the purge gas flow during the process. The technical effect of this patent is the creation of a block of polyolefin material with uniform crosslinking, which can be used in various applications such as the production of pipes and wires.

Problems solved by technology

These are deficient in that they either change the chemical composition of the polymer or create short polymer chains.

The major drawback of this method is that the resultant material often has a different chemical composition than that of the starting material due to the inclusion of the crosslinking agent.

The non-uniformity arises from the radiation dose distribution in the polymer.

The second major shortcoming is that irradiation penetration from the surface of the polymer may not be thorough.

For e-beam irradiation, the limited power of penetration results in a higher dose near the surface while lower or zero dose in the interior.

The third major shortcoming is that crosslinking reactions of free radicals are often incomplete; leaving residual free radicals in the material that can cause oxidation or other chemical changes during storage or field applications.

It is well known that material properties are deteriorated when a polymeric material is oxidized.

Short chain formation tends to weaken the material strength as the effective molecular weight is reduced.

Images